Production of crimped yarns



Ott. 15, MEL" N H R ET AL 3,405,517

PRODUCTION OF CRIMPED YARNS Filed June 30, 1966 2 Sheets-Sheet 1 :r: F. o z m a: an

l j l -30 -20 -10 0 l0 FEED RATIO l I l -30 -20 -IO 0 l0 FEED RATIO INVENTORS MEIJI ANAHARA TADAO EZAKI KAZUMI NAKAGAWA NOBUHlRO TSUTSUI TAKESHI OKAZAKI BY run/a4 2,1 1* @1406 E ATTORNEYS Oct. 15, 1968 MEL ANAH R ETAL 3,405,517

PRODUCTION OF CRIMPED YARNS Filed June 30, 1966 2 Sheets-Sheet 2 FEED RATIO 1 INVENTORS MEIJI ANAHARA TADAO EZAKI KAZUMI NAKAGAWA NOBUHIRO TSUTSUI TAKESHI OKAZAKI BY UM, #4 PM ATTORNEYS United. States Patent 01 fice 3,405,517 Patented Oct. 15, 1968 1 Claim. c1: 57-457 ABSTRACT OF THE DISCLOSURE A method for manufacturing crimped acrylonitrile continuousfilament yarn comprising forwarding a continuous filament acrylonitrile yarn to a false twisting apparatus, subjecting the yarn to a false twisting operation and withdrawing the yarn from the false twisting apparatus, the improvement according to which the acrylonitrile filament is treated at the feed ratio (R%) represented bythe formula wherein X is the residual shrinkage of said filament yarn in a saturated steam at 125 C.

The present invention relates to a continuous synthetic bulky yarn having improved crimp characteristics and made predominantly of acrylonitrile and a method of making the same. More particularly, the invention relates to a method of making a superior bulky crimped yarn, the crimp of which is extraordinarily durable to hot wet conditions.

Various proposals have heretofore been made as to the means of crimping thermoplastic synthetic continuous filament yarns and some of the proposals have been carried into practice. In essence, these methods consist in thermally setting the continuous filament yarns when it remains bent or twisted. As one of continuous crimping methods, a false-twisting has been carried out, but it consists of the steps of giving a high twist to the continuous filament yarns temporarily, heat-setting the same, untwisting it, and, finally, winding it up. In this manner, the deformation of the monofilaments set in such a highly twisted state gives rise to an intricate spiral configuration after untwisting and the consequent loss of the parallel arrangement of the monofilaments yields the desired bulk in the yarn.

As the conditions of such false twisting method, Japanese patent publication No. 1397/57, for instance, describes a method in which the feed speed of continuous filament yarns at the inlet of the false-twisting machine is lower than the speed of withdrawal at the outlet of the machine to the extent that the continuous filament yarns is stretched 0.5 to 20 percent. On the other hand, it has been proposed, as in Japanese patent publication No. 8612/62, to arrange the operation so that the feed speed is about 3 to 35 percent higher than the speed of withdrawal. These two sets of conditions contradict each other, and if both are right, it is of no significance if the feed speed is higher or lower than the speed of withdrawal so long as the false-twisting of thermoplastic synthetic fiber is concerned. As a corollary, it seems a fruitless effort to limit, in any way, the ratio of feed speed to withdrawing speed in the false-twisting machine.

Starting from the above proposition, we have conducted an investigation with acrylonitrile continuous filament yarns and arrived at the finding that the physical properties, especially thermal behaviours, have an important bearing on the optimum false-twisting conditions. The present invention represents a culmination of the above investigation and finding.

Among various steps in the production of synthetic acrylonitrile continuous filaments, it has been known that the steps which most vitally affect its physical properties, particularly, its thermal behavior such as residual shrinkage are hot-drawing and heat-treating under no tension (i.e. relaxation) or heat-treating under tension (i.e. heatsetting).

Hot-drawing is necessary in order to give sufficient strength to the filament, while either relaxation or heatsetting which is usually conducted under dry hot or wet hot conditions, imparts toughness and thermal stability to the filament.

The filaments which have not been relaxed or heat-set, as well as filaments which have been only mildly heat-set or mildly relaxed or the filament which has been heat-set and, then, hotstretched, is thermally unstable and, when heat-treated in a free state, shrinks in a substantial measure. In contrast, filaments which have been hot-stretched and then, sufiiciently relaxed or heat-set are thermally stable and, even if heat-treated in a free state, would shrink only little or not shrink at all. Thus, the residual shrinkage of acrylic filament varies with the heat treatment conditions prior to the false twisting stage.

The residual shrinkage is usually represented by the rate of shrinkage of a sample filament as measured in hot water at 100 C., but as the factor that relates the proper range of feed ratios to be adopted in the false-twisting method of this invention with the thermal history of acrylic filament employed, it has been found most suitable to use the residual shrinkage value for 125 C.

The residual shrinkage at 125 C., mentioned immediately above, is the rate of shrinkage of an acrylic filament as measured after it is heat-treated in a free state in saturated steam at 125 C. for 5 minutes, and the greater the value found, the less thermally stable is the filament so treated.

. The feed ratio mentioned above is the ratio of the speed of feeding to the speed of withdrawal of continuous filament yarns in the false-twisting process and is represented by the following equation:

Speed of feed- Speed of Withing (m./rnin.) drawal (rn./rnin.)

Feed mtlo Speed of withdrawal (m./min.)

In the accompanying drawings: v

FIG. 1 is a diagram showing the strength of falsetwisted yarn;

FIG. 2 is a diagram showing the elongation of falsetwisted yarn;

FIG. 3 is a diagram showing the degree of crimp stretchability of false-twisted yarn; and

FIG. 4 is a diagram showing the number of imperfectly untwisted parts in false-twisted yarn.

In the case of synthetic acrylic filament yarns, the following general rules hold: The lower the feed ratio used, the lower the strength and elongation of the falsetwisted filament (See FIGS. 1 and 2), and the more liable are the monofilaments to break in the course of falsetwisting, thereby adversely affecting the operating efiiciency, although the resistance of the crimp to hot wet conditions is improved as illustrated in FIG. 3.

FIG. 3 shows the degree of crimp stretchability of false twisted filament yarn as measured after the sample yarn is held under a load of 0.25 mg./d. and in saturated steam at C. for 20 minutes.

The degree of crimp stretchability is an important index, with which the durability of crimp may be determined, and the greater the index value, the more durable is the Degree of crimp stretchability 100 (wherein I is the length of yarn under the initial load of 1 mg./d., and is the length of yarn under the load of 100 mg./d.).

Generally speaking, as the feed ratio increased, it becomes more and more difiicult to nntwist the warn completely and, as shown in FIG. 4, there remains many imperfectly untwisted parts in false twisted yarn, resulting in a substantial debasement of yarn quality; The number of imperfectly untwisted parts as indicated in FIG. 4 is the number of said imperfectly untwisted parts found for every 40 meters of yarn.

It will be apparent from the above description that there is a suitable range of feed ratios to be adhered to as one of the conditions under which continuous filament yarns are false-twisted. The suitable feed ratio, explained above, depends on the degree of residual shrinkage of the acrylic filament to be false-twisted, and a limited range of feed ratio (R) must be adhered to in order to obtain a falsetwisted acrylic filament yarn having an adequate strength, almost none of imperfectly untwisted parts and a crimp durability to hot wet conditions. Thus, the suitable feed ratio R( may be written as follows TABLE 1 Sample Residual shrinkage Optimum feed ratio at 125 0. (percent) (percent) As for the other false-twisting conditions, the temperature of the heating pipe should be somewhere between 180 C. and 205 C. If acrylic continuous filament yarn is treated at temperatures below 180 C., the final crimp will not be as durable to hot wet conditions as desired. When the temperature exceeds 205 C., the quality of the processed yarn is degraded, for it tends to be discolored or become fused, for instance.

The synthetic acrylic filament yarn false-twisted as above does not lose its rich crimp through all the subsequent dyeing and other steps, and the fabric, whether knit or woven, of such a yarn has a good bulk and a supple hand as contrasted with the slick feed of the conventional product of this type. These are superior characteristics not found in other thermoplastic fibers products. It need not to be mentioned that the above characteristics also apply to the dope dyed yarn.

This invention will be further described hereinafter by way of the following examples, in which all percents are by weight.

Example 1 A copolymer (molecular weight: 75,000) composed of 91% acrylonitrile, 8.6% methyl methacrylate, and 0.4% allylsulfonic acid is dissolved in 44% aqueous solution of sodium rhodanate to prepare a spinning dope (polymer concentration: 11%). The spinning dope is extruded in 10% aqueous solution of sodium rhodanate at 3 C. through a nozzle (50 orifices. each measuring 0.09 mm. in

diameter). The resulting tow is washed with. water thoroughly to remove the sodium rhodanate and, then, hot-stretched in saturated steam at 110 C. to 1300% its initial length. By-passing the relaxation step, the filament is treated with an antistatic agent. After drying, the filament is wound up on a bobbin at the rate of meters per minute. The total denier of the resulting filament yarn is 150 d., and its residual shrinkage as measured in saturated steam at 125 C. is 27%. This acrylic continuous filament yarn is fed into a false-twisting machine of the conventional type (Sotexa, SWIDPM type, France) wherein it is processed at a temperature of 185 C. (the number of twists minus 1800 per meter: the feeding ratio -3.3%). Under the conditions just mentioned, the continuous filament yarns can be processed quite satisfactorily without troubles such as breaking and the formation of imperfectly untwisted parts. The falsetwisted yarn is held under a constant load of 0.25 mg./d. in the air at 90 C. for 20 minutes. The degree of crimp stretchability of this yarn is 39%. When the same yarn as above is held under the load of 0.25 mg./d. in saturated steam at C. for 20 minutes, the crimp stretchability value is 21.3%. On the other hand, when an arbitrary feed ratio, e.g. 11.7%, is adopted, imperfectly untwisted parts are too numerous and the degrees of crimp stretchability of the yarn as measured after treatments under the load of 0.25 mg./d. in the air at 90 C. for 20 minutes and in saturated steam at 110 C. for 20 minutes are 31.5% and 8.8%, respectively. It is apparent, therefore, that the acrylic filament yarn processed at the optimum feed ratio mentioned above is superior to the yarn otherwise processed.

Example 2 A copolymer (molecular weight: 58,000) composed of 89.6% acrylonitrile and 10.4% methyl methacrylate is dissolved in 44% aqueous solution of sodium rhodanate to prepare a spinning dope (polymer concentration: 11%). This spinning dope (polymer concentration: 11%) is extruded in 10% aqueous solution of sodium rhodanate at -3 C. through a spinning nozzle (70 orifices, each measuring 0.09 mm. in diameter). The resulting tow is washed with water thoroughly to remove the sodium rhodanate and, then, stretched in boiling water to 1200% its initial length. The continuous filament yarn is treated with an antistatic agent and, after drying, caused to shrink by 18% on hot plates at 200 C. The shrunken continuous filament yarn is finally wound up on a bobbin at the rate of 300 meters per minute. The resulting continuous filament yarn has a total denier of 175 and its residual shrinkage at 125 C. is 17.2%. This acrylic continuous filament yarn is false-twisted at the optimum feed ratio of --l5% under the same conditions as Example 1 except the feed ratio. Under these conditions, the operation can be satisfactorily carried out without troubles such as breaking and the formation of imperfectly untwisted parts. After this yarn is subjected to a load of 0.25 mg./d. in the air at 90 C. for 20 minutes, its degree of crimp stretchability is 40.5%. Even after this yarn is subjected to a load of 0.25 mg./d. in saturated steam at 110 C. for 20 minutes, its degree of crimp stretchability is 19.8%. On the other hand, when an arbitrary feeding ratio, e.g. 0%, is adopted for false-twisting, imperfectly untwisted parts are too numerous and when the same yarn is subjected to a load of 0.25 *mg./d. in saturated steam at 110 C. for 20 minutes, its degree of crimp stretchability is 8.0%.

Example 3 Before the same acrylic continuous filament yarns as the one used in Example 2 is false-twisted, it is stretched to its initial length by causing it to come in contact with hot plates at 180 C. The residual shrinkage of this filament in saturated steam at C. is 22%. When the same fiber is false-twisted with the optimum feed ratio of 6.6% under the same conditions except feed ratio are same as Example 1, the operation can be satisfactorily carried out without troubles such as the formation of imperfectly untwisted parts. The yarn processed as above is then subjected to a load of 0.25 mg./d. in hot air streams at 90 C. for 20 minutes. After this treatment, the crimp stretchability of the yarn is 37.0%. The corresponding figure is 21.3% after the same yarn is subjected to a load of 0.25 mgJd. in saturated steam at 110 C. for 20 minutes.

Example 4 A copolymer (molecular weight: 63,000) composed of 90.5% acrylonitrile, 9.2% methyl methacrylate, and 0.3% allylsulfonic acid is dissolved in 45% aqueous solution of sodium rhodanate to prepare a spinning dope (polymer concentration: 10.5%). This spinning dope is extruded in aqueous solution of sodium rhodanate at 3 C. through a spinning nozzle (50 orifices, each measuring 0.085 mm. in diameter). The tow is washed with water to completely remove the sodium rhodanate and, then, stretched in boiling water to 1200% its initial length. The continuous filament yarn is treated with an antistatic agent and, after drying, caused to shrink by 13% on hot plates at 200 C. The continuous filament yarn is wound up on a bobbin at the rate of 300 meters per minute, and the continuous filament yarn and bobbin is heat-treated in saturated steam at 125 C. for 20 minutes. The total denier of the resulting fiber is 150 d., and its residual shrinkage at 125 C. is 7.8%. This acrylic continuous filament yarn is false-twisted at the optimum feed ratio of -23.3% under the same conditions as Example 1 except for feed ratio. Under these conditions, the operation can be quite satisfactorily carried out without troubles such as breaking and the formation of imperfectly untwisted parts. After the yarn is subjected to a load of 0.25 mg/d. in the air at C. for 20 minutes, its crimp stretchability is 34%. The corresponding figure is 19% after the same yarn is subjected to a load of 0.25 mg./d. in saturated steam at C. On the other hand, when an arbitrary feed ratio, e.g. -10%, is adopted for false-twisting, imperfectly untwisted parts are too numerous and the crimp stretchability of the yarn is 6% after it has been subjected to a load of 0.25 mg./d. in saturated steam at 110 C. for 20 minutes.

What we claim is:

1. In a method for manufacturing crimped acrylonitrile continuous filament yarn comprising forwarding a continuous filament acrylonitrile yarn to a false twisting apparatus, subjecting the yarn to a false twisting operation and withdrawing the yarn from the false twisting apparatus, the improvement according to which the acrylonitrile filament yarn is treated at a feed ratio (R%) represented by the following formula:

wherein X is the residual shrinkage of said filament yarn in a saturated steam at -l25 C.

References Cited UNITED STATES PATENTS 3,077,724 2/ 1963 Stoddard et al. 57-34 JOHN PETRAKES, Primary Examin r.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3 405 5 l7 Dated October l5 1968 Invent0r(s) Me ii i ANAHARA, 'I'adao EZAKI Kazumi NAKAGAWA,

Nobuhiro TSUTSUI and Takeshi OKAZAKI It is certified that error a ppears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, last line of claim 1, "l25C" should read 125C Signed and sealed this 22nd day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

